Tides and Waves Flashcards
Tides,
what are tides?
the alternate rise and fall of the level of the sea
what are tides caused by?
the gravitational pull of the moon and partly by the sun
when do high tides occur?
when the moon and sun are in alignment, there is the biggest gravitational pull.
when are storm surges created?
- high tides
- strong onshore winds
- high levels of wave energy
- low pressure weather systems
- low lying coastlines experience the worse
what are waves?
they are simply energy moving through water
what does the wave size depend on?
the strength of the wind, the duration the wind blows for, water depth and wave fetch.
where are the UK’s largest waves?
In Cornwall, they have travelled 4,000 km across the Atlantic Ocean from Florida, there is a long fetch.
how can wave fetch cause different rates of coastline recession?
- the longer distance waves have travelled, the more energy they have, meaning they are more powerful, increasing erosion. this increases hydraulic action and abrasion
describe how a wave breaks
-friction between the sea bed begins to distort the wave par tide orbit from circular to elliptical and slows the wave down.
-the wave depth decreases, and velocity slows
-crest begins to move forward faster than the trough
-crest outruns the trough so the wave breaks
what is a swash?
the wave breaks in nearshore zone and water flows up the beach
what is a backwash?
the wave loses energy and gravity pulls the water back down the beach
features of constructive waves
-low wave in proportion to length
-weaker backwash
-stronger swash
-the wave ‘spills’
-there is a ridge
-the wave deposits and builds up beaches
-increases the gradient of the beach in its lower section
features of destructive waves
-high wave in proportion to length
-stronger backwash
-weaker swash
-the wave ‘plunges’
-there is a steep profile
-the wave destroys the beach and erodes
-the beach profile becomes gentler in its lower section
wave length
the average distance between a successive wave crests
wave height
the vertical distance between a wave trough and wave crest
